The present invention relates to carbapenem antibacterial agents in which the carbapenem nucleus is substituted at the 2-position with fused bi- and tricyclic 2,2-dioxo-3-X-2-thia-1-aza-cyclopenta ring systems linked through a CH.sub.2 group.
The carbapenems of the present invention are useful against gram positive microorganisms, especially methicillin resistant Staphylococcus aureus (MRSA), methicillin resistant Staphylococcus epidermidis (MRSE), and methicillin resistant coagulase negative Staphylococci (MRCNS). The antibacterial compounds of the present invention thus comprise an important contribution to therapy for treating infections caused by these difficult to control pathogens. There is an increasing need for agents effective against such pathogens (MRSA/MRCNS) which are at the same time relatively free from undesirable side effects.